<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <meta http-equiv="X-UA-Compatible" content="ie=edge">
  <title>border做icon</title>
</head>

<body>
  <div class="icon-add"></div>
  <div class="icon-add icon-add2"></div>
  <style>
    .icon-add {
      color: #999;
      border: 1px solid;
      width: 200px;
      height: 200px;
    }
    .icon-add2{
      border-radius: 50%;
    }
    .icon-add:hover{
      color: #333;
    }
    .icon-add::before,
    .icon-add::after {
      content: "";
      display: block;
    }

    .icon-add::before {
      height: 100px;
      border-left: 10px solid;
      margin-left: 95px;
      margin-top: 50px;
    }

    .icon-add::after {
      width: 100px;
      border-top: 10px solid;
      margin-left: 50px;
      margin-top: -55px;
    }
  </style>
</body>

</html>